Results from seven-country project indicate that pneumonia kills 900,000 children under five years old and more than 100 million cases reported each year worldwide.
According to the study from a consortium of scientists from around the world, led by a team at the Johns Hopkins Bloomberg School of Public Health, United States, this makes pneumonia a greater cause of childhood mortality than malaria, but tuberculosis (TB), Human Immuno-deficiency Virus (HIV), Zika virus and Ebola virus combined.
The study embargoed to be published today in The Lancet journal highlights need for new vaccines, especially against respiratory syncytial virus.
Respiratory syncytial virus (RSV) and other viruses now appear to be the main causes of severe childhood pneumonia in low- and middle-income countries, highlighting the need for vaccines against these pathogens.
The study is titled “Causes of severe pneumonia requiring hospital admission in children without HIV infection from Africa and Asia: the PERCH multi-country case-control study.”
The study was carried out at sites in Bangladesh, The Gambia, Kenya, Mali, South Africa, Thailand, and Zambia.
The study was the largest and most comprehensive of its kind since the 1980s. It included nearly 10,000 children in seven African and Asian countries. After testing for viruses, bacteria, and other pathogens in children with severe hospitalized pneumonia—and in community children without pneumonia—the study found that 61 percent of severe pneumonia cases were caused by viruses led by RSV, which alone accounted for 31 percent of cases.
Study co-principal investigator Maria Deloria Knoll, PhD, a senior scientist in the Bloomberg School’s Department of International Health, and associate director of science at the Johns Hopkins International Vaccine Access Center (IVAC), said: “Prior to this study, we didn’t know which specific viruses and bacteria are now causing most of the severe childhood pneumonia cases in the world, but public health organizations and vaccine manufacturers really need that information to work toward reducing the substantial childhood mortality that pneumonia still causes.”
According to the researchers, identifying the germs that cause pneumonia is difficult in individual cases and much more so on a scale of thousands of cases, especially in low- and middle-income countries where most pneumonia deaths occur.
Researchers in prior pneumonia studies simply lacked the microbiological and analytical resources to produce estimates of the major pneumonia pathogens, Knoll says. And, in the past two decades, many low- and middle-income countries have introduced effective vaccines against known major bacterial causes of pneumonia—Haemophilus influenzae type b and Streptococcus pneumoniae—so the global mix of pathogens causing childhood pneumonia has changed as a result.
The new, IVAC-led study, known as the Pneumonia Etiology Research for Child Health (PERCH) study, included 4,232 cases of severe hospitalized pneumonia among children under five years and 5,325 community children without pneumonia during a two-year period.
PERCH was supported by grant 48968 from The Bill & Melinda Gates Foundation.
For their study, researchers took nasal and throat swabs as well as blood, sputum and other fluid samples from cases and controls and tested them for pathogens using state-of-the-art laboratory techniques. Cases for the primary analysis were limited to those whose pneumonia was confirmed by chest X-ray, and children with HIV were considered in a separate analysis because the causes of their pneumonia would likely differ from those without HIV.